Process for the manufacture of crimped yarn



Dec. 31, 1963 c. c. NOTT 3,115,744

PROCESS FOR THE MANUFACTURE OF CRIMPED YARN Filed July 22, 1960 InventorCome/v 619/9245: /Varr Attorneys United States Patent M 3,115,744PROCESS FGR THE MANUFACTURE OF CRIMPED YARN Conan Charles Nott, TownCentre, Cwrnbran, England,

assignor to British Nylon Spinners Limited, Pontypool,

England Filed July 22, 1960, Ser. No. 44,597 Claims priority,application Great Britain July 24, N59 6 Claims. (Cl. 57-157) Thisinvention relates to yarn comprising synthetic linear polymers, and moreparticularly to yarn consisting of or containing a synthetic linearpolyamide, and to processes for manufacturing said yarn.

The present yarn consists of continuous filaments; it is composed atleast mainly, of a synthetic linear polymer of the type which can bemelt-spun, for example, a polyamide or a polyester. The filaments mayconsist wholly of polyhexamethylene adipamide, but other syntheticlinear polymers may form the material of the filaments, for instance,polyureas, e.g. polyhexamethylene urea, polyurethanes, e.g.polybutylene. glycol hexamethylene dicarbamate, polyesters, e.g.polyethylene terephthalate, stereospecific polyolefines, e.g.polypropylene or the following polyamides namely, polyhexamethylenesebacamide, polykappa-aminoundecanoic acid, poly-epsilon-caprolactam.The yarn of the present invention may thus include filaments of othertextile material besides synthetic linear polymers provided that thelatter constitute at least the major proportion of said yarn.

Yarn consisting of synthetic linear polymer filament, for example, apolyamide yarn made of polyhexamethylene adipamide, possesses manyproperties eagerly sought after for textile purposes and, in particular,a high degree of strength expressed as the tenacity at the point ofrupture. Such yarn is accordingly manufactured commercially on a largescale, the high tenacity being attained by submitting the filaments to aprocess of drawing whilst they are in the solid state, a processfrequently referred to as cold-drawing. Thus the filaments, in theirundrawn condition after being solution-spun or melt-spun from therequired polymer, are elongated in the solid state, commonly by passagebetween two pairs of rolls, the second pair revolving faster than thefirst. Between the rolls the filaments may, if desired, pass round asnubbing pin so as to locate the point at which drawing takes place.

During the last decade the employment of synthetic linear polymer yarn,notably polyamide yarn and later polyester yarn, in various textilefields formerly depending on natural fibres or conventional rayon yarnsuch as viscose or cellulose acetate, has continuously increased. Yarncomposed of a synthetic linear polymer possesses numerous excellentproperties among which high tenacity, resistance to abrasion anduniformity are especially to be reckoned. Nevertheless such yarn is aptto be regarded, in the case of some end uses, as inadequate or capableof improvement in respect of aquality known as handle, feel, loftiness,bulk or fullness, a characteristic which is not easy to define becauseit is largely subjective and consequently a matter of personal opinion.The reason for the lack of bulk or fullness seems to reside at least insome measure in the normal smoothness of synthetic linear polymerfilaments. Be this as it may, however, this quality of fullness is ofgreat importance because it is understood to be related to the power offabrics made from the yarn to absorb moisture and afford warmth.Consequently efforts have frequently been made in the past, to enhancethe fullness of synthetic linear polymer yarn, by increasing its bulk bymeans of numerous crimping processes or by giving it a hairy or fuzzynature in various ways. Yet it is ditficult to obtain quite the desiredeffect. For not only must the yarn present the right 3,115,744 PatentedDec. 31, 1963 appearance to the eye and possess the correct feel, but itis essential that it have the necessary mechanical properties as well.For example, a crimped yarn of suitable fullness and appearance, maylose these qualities on being wovenowing to the tension exerted in theloom pulling out the crimps. Hot wet treatment. as, for instance, indyeing, is also liable to interfere with the physical nature of theyarn.

The present invention concerns a new process for producing a full orlofty synthetic linear polymer yarn starting with undrawn yarn, whichdepends on the incorporation in the drawing process of a heat treatmentwhereby part of the yarn when it has been drawn, is subjected to araised temperature, the yarn being held substantially at constant lengthduring the heat treatment. The heated part of the yarn then has areduced tendency to shrink; in other words it is dimensionally morestable than the other part. After the two parts are twisted together andshrunk, the heated part of the yarn forms loose convolutions around theunheated part which remains substantially straight. If desired, aplurality of different heat treatments may be provided so as to subjectvarious parts of the yarn to different raised temperatures.

The undrawn yarn may be twistless; but in any case it is essential thatthere should be no twist between those parts of the yarn which must beparted from each other in the form of separate strands to permit them tobe given different heat treatment, or no heat treatment.

Accordingly this invention relates to a process for the manufacture ofyarn comprising drawing undrawn or incompletely drawn synthetic linearpolymer multifilarnent yarn between a feed roll and draw roll, whichprocess is characterised in that the yarn after passage round the feedroll and the draw roll, is separated into two or more parts, which partsare subjected to different temperatures whilst their length ismaintained substantially constant, the parts of the yarn being thentwisted together by conventional means.

If desired, the undrawn or incompletely drawn multifilament yarn maycomprise filaments of more than one denier. In the case of two deniers,when only the lighter denier filaments are heated after drawing, theheavier denier filaments shrink more and when the heated and unheatedparts of the multifilament yarn are twisted together or doubled, theheavier denier part forms a core which is clad by the filaments oflighter denier.

The separation of the yarn may, for example, be effected by providingthe draw roll with two separator rolls, so that the yarn, after passageround the feed roll and the draw roll and one of the separator rolls, isseparated into two parts, one of which continues to run round theaforesaid separator roll and draw roll, whilst the other part of theyarn then runs round the draw roll and the second separator roll, and issubjected during its passage between these two rolls to a heat treatmentwhilst its length *is maintained substantially constant.

Another way of separating the yarn is by spreading" it out as a ribbon,so that only part of the ribbon may receive the heat treatment. In thiscase the separate strands, though distinct, are adjacent. It has alreadybeen stated that the yarn may be divided into more than two parts forthe purpose of various heat treatments; in such cases the draw roll isequipped with a corresponding number of separator rolls when this methodof separating the yarn is employed.

As already indicated, a snubbing pin, if desired, be located between thefood roll and the draw roll.

The invention includes yarns manufactured in accordance with the aboveprocess.

The heat treatment can be applied by causing the yarn to run over a hotplate so as to subject it to the required temperature. Some other meansfor heating the yarn are hot nitrogen, steam, infra-red radiant heat,hot molten metal or a high frequency electrical field. It is evidentthat the temperature reached must not be so high as to melt the polymer,and the melting points of the polymers already mentioned above aretherefore now quoted as a guide:

C. Polyhexamethylene adipamide 248 Polyhexamethylene urea 270Polybutylene glycol hexamethylene dicarbamate 178 Polyethyleneterephthalate 255 Stereospecific polypropylene 165 Polyhexamethylenesebacamide 209 Poly-kappa-a-minoundecanoic acid 187Poly-epsilon-caprolactam 2l4 It will be understood that when the yarn isreferred to as passing round the feed roll, and the like, the yarn maymake one or more turns or wraps round the said roll in accordance withknown textile practice.

The fullness or bulk of the present yarn is enhanced or its developmentaccelerated by heating the yarn, especially in the presence of water,egg. by immersion in water at 60 C. or by steaming. The inventionincludes the bulked yarn when so treated. Its loftiness is stable totension. When the yarn is first woven into a fabric and the fabric thenheated in the aforesaid manner, a crepe effect is produced.

The yarns of the present invention may be, if desired, subsequentlydoubled, braided, looped, set by heat, hot water or steam, dyed, sizedor otherwise conventionally treated to prepare them for use in knitting,warp-knitting, weaving or other textile manufacturing process. Theseyarns are eminently suited for blouses or lingerie.

One embodiment of the process according to the invention is illustratedby the accompanying diagrammatic drawings wherein the numbers have thefollowing meanlngs:

When the present process is operated, the undrawn yarn 10 is passedbetween the nip roll 1 and feed roll 2 and then round the snubbing pin3; thence it goes around the draw roll 4 and separator roll 5 once orseveral times. When the yarn arrives at point 111 it is separated intotwo parts, one part continuing to run around rolls 4 and 5 whilst theother part passes to separator roll 6 and back over the hot plate '7 tothe draw roll 4. The two parts of the original yarn, reunited, thentraverse the guide 8 and are wound up and twisted at 9.

The following examples which are by way of illustrating but not limitingthe invention describe some specific ways in which the above apparatuscan be operated.

Nip roll Feed roll Snubbing pin Draw roll First separator roll Secondseparator roll Electrically heated hot plate Yarn guide Conventionalbobbin for winding up yarn Yarn Example 1 An undrawn yarn comprising twomultifilament strands (not twisted together), each strand containing 60filaments and having turn per inch 2 twist, is drawn at 90 feet perminute and at a mechanical draw ratio of 4.06 by means of the apparatusdescribed above.

The yarn path is as follows. The yarn, after passing between rolls 1 and2 and twice around the snubbing pin 3, goes three times round rolls 4and 5. The yarn has now been drawn. At point 11 the two strands areseparated; One continues to pass round rolls 4 and 5, making three morecircuits. The other strand is taken thrice round rolls 4 and 6. Thisstrand passes over the hot plate 4 7 which is 6 inches long andmaintained at 160 C. Thus the total number of wraps on the draw roll is6.

The yarn is finally wound up and given 4.3 Z turns per inch twist at 9after passing through the yarn guide 8. When relaxed in hot water (60C.) the yarn is found to be full and has a good handle. Its denier is2624.

Example 2 An undrawn yarn of polyhexamethylene adipamide, comprisingfour strands, each of 60 filaments twisted with 34, 2 turn per inch isdrawn at feet per minute at a mechanical draw ratio of 4.06 as inExample 1, with the use of the same apparatus as therein referred to.

All four strands proceed 3 times round rolls 4 and 5. At point 11 two ofthe strands are separated from the other two, one pair making three morecircuits round rolls 4 and 5 and the other pair going thrice round rolls4 and 6 and over the heater 7. The strands are then united and wound upand twisted (4 2 turns per inch).

The resultant yarn is finally steamed under negligible tension, when abulked yarn of pleasant handle results. Its denier is 5764.

Example 3 An undrawn yarn of polyhexamethylene adipamide comprises twostrands, each consisting of 60 filaments twisted together with turn perinch. The total denier is 826.

The yarn is drawn on the apparatus previously described except that thesnubbing pin 3 is omitted. The mechanical draw ratio is 3.09 and thetemperature of the hot plate is 200 C. One strand is passed six timesround rolls 4 and 5, the other strand three times round rolls 4 and 5and three times round rolls 4 and 6. The combined strands are wound upand given 2 /2 2 turns per inch twist.

The resulting yarn which has a denier of 285 is woven as weft against awarp consisting of a polyhexamethylene adipamide yarn of 34 filaments(total denier twisted with 7 turns per inch 8 twist.

The resulting fabric is immersed in an aqueous bath containing 0.2%sodium carbonate and 0.2% soap at room temperature. The bath is heatedup to 60 C. during 30 minutes and maintained at this temperature for afurther 30 minutes. The fabric is rinsed and dried; it possesses awell-defined crepe effect.

The fabric is heat set by submitting it to a temperature of 215 C. for'27 seconds on a stenter, adjusted to permit 3% shrinkage in both thewarp and weft directions.

The fabric is subsequently dyed with Multamine Navy Blue 28 (obtainablefrom Imperial Chemical Industries, Ltd.) and retains its crepeappearance.

Example 4 A yarn comprising six strands of polyhexamethylene adipamideeach containing filaments twisted together with Z turn per inch, isdrawn on a conventional drawing machine, that is, as illustrated in theaccompanying drawing, the roll 6 and the heater 7 being absent.

The rate of drawing is 325 feet per minute and the mechanical draw ratiois 5.45.

The yarn comprising the six strands forms on the draw roll a ribbon 1%inches wide. The yarn is taken round the draw roll 4 and separator roll5 six times, but during the fourth circuit the yarn makes contact with a10 inch long plate maintained at C. which is suitably positioned so thatonly half the ribbon of yarn i.e. A5 inch actually passes along the hotplate in contact therewith. The yarn is then twisted and wound up thetwist inserted being 4% Z turns per inch. On relaxing the resultingdrawn yarn in water at 60 C., a bulked yarn having a total denier of5875 is obtained.

Example 5 An untwisted undrawn yarn of polyhexarnethylene adipamidecomprising 34 filaments of 40 denier and 10 filaments of 50 denier (thetotal denier being 353) is drawn to 3.92 times its original length at210 feet per minute on the same apparatus as that employed in Examples 1and 2.

The whole yarn is passed 3 times round rolls 4 and 5. At point 11 thestrand of lower denier is separated from that of heavier denier, thelatter making 3 more circuits round rolls 4 and 5. The strand of lowerdenier passes from point 11 round roll 6, over the heater 7 and thentwice round rolls 4 and 5. The two strands are combined and wound up at9 with the insertion of 2 2 turns per inch twist. When relaxed in hotwater (60 C.) the yarn becomes full and of a good handle, the strand ofheavier denier tending to form a core which is clad by the strand oflighter denier.

What we claim is:

1. Process for the manufacture of yarn comprising: drawing continuousincompletely drawn melt-spun synthetic linear polymer multifilamentyarn; separating the yarn into at least two strands; heating one of saidstrands to a temperature between slightly below its melting point and atemperature at which the tendency of the strand to shrink is reduced asubstantial amount while maintaining its length substantially constant;simultaneously maintaining the other strand at a lower temperature thanthat to which said one strand is heated so that said other strand has atendency to shrink which is greater than the tendency of said one strandto shrink; and twisting together said strands to form a yarn.

2. Process for the manufacture of yarn as claimed in claim 1 wherein theincompletely drawn mul-tifilament yarn comprises filaments of more thanone denier.

3. Process for the manufacture of yarn as claimed in claim 1 whereinsaid one strand is heated by passage over a hot plate.

4. Process for the manufacture of yarn as claimed in claim 1 wherein theyarn, after the parts thereof have been twisted together, is heat-shrunkso as to become full or bulked.

5. Process for the manufacture of yarn as claimed in claim 4 wherein thestep of heat-shrinking the yarn includes heating the yarn in thepresence of water.

6. Process for the manufacture of yarn comprising: drawing continuousincompletely drawn melt-spun synthetic polymer multifilament yarn;separating the yarn into at least two strands; reducing the tendency ofone of the strands to shrink by passing the same over a heated solidsurface to heat it to a temperature between slightly below its meltingpoint and a temperature at which the tendency of the strand to shrink isreduced a substantial amount while maintaining its length substantiallyconstant; simultaneously maintaining the other strand at a lowertemperature than that to which said one strand is heated so that saidother strand has a tendency to shrink which is greater than the tendencyof said one strand to shrink; twisting together the strands to form ayarn; heating the yarn in the presence of water to cause the previouslyheated strand to form loose convolutions around the previously unheatedstrand thereby forming a bulked yarn.

References Cited in the file of this patent UNITED STATES PATENTS2,174,878 Hardy Oct. 3, 1939 2,789,340 Cresswell Apr. 23, 1957 2,855,749Eshuis Oct. 14, 1958 2,956,330 Pitzl Oct. 18, 1960 2,979,883 Waltz Apr.18, 1961 2,985,940 Weldon May 30, 1961

1. PROCESS FOR THE MANUFACTURE OF YARN COMPRISING: DRAWING CONTINUOUSINCOMPLETELY DRAWN MELT-SPUN SYNTHETIC LINEAR POLYMER MULTIFILAMENTYARN; SEPARATING THE YARN INTO AT LEAST TWO STRANDS; HEATING ONE OF SAIDSTRANDS TO A TEMPERATURE BETWEEN SLIGHTLY BELOW ITS MELTING POINT AND ATEMPERATURE AT WHICH THE TENDENCY OF THE STRAND TO